The use of phonon and plasmon interface modes as diagnostic tools for characterising low dimensional semiconductor structures

Far infrared Fourier transform spectroscopy is a well-established technique for investigating the dielectric response functions of phonons and plasmons in bulk and low-dimensional semiconductors. The vibrational properties of binary solids like the III-V and II-VI compound semiconductors are described quite well by a simple linear chain model which leads to a good description of the optical and acoustic branches of the phonon dispersion curves. In the long wavelength limit the model can be further developed to describe the polariton coupling between the photons and the optical phonons. This coupling leads to the-well-known reststrahlen band of high reflectivity between the transverse optic phonon frequency, /spl omega//sub TO/, and the longitudinal optic phonon frequency, /spl omega//sub LO/. The interface modes discussed here occur in the region of /spl omega//sub LO/.